Prevention of bone loss and improvement of pain-related behavior in hind limb-unloaded mice by administration of teriparatide and bisphosphonate

Abstract

Objectives

There are few reports on the comparison between teriparatide (PTH) and bisphosphonate (BP) in terms of osteoporosis pain-related behavior and immunohistochemical findings. The aims of this study were to evaluate skeletal pain associated with osteoporosis and to examine the inhibitory effect of PTH and BP on pain and bone loss in hind limb-unloaded (HU) mice. The mechanism of osteoporotic pain in HU mice was evaluated by examining pain-related behavior and immunohistochemical findings. The effects of PTH and alendronate (ALN), a potent osteoclast inhibitor, on these parameters were also assessed.

Methods

Eight-week-old male ddY mice were tail-suspended for 2 weeks and assigned to four groups: hind limb-loaded (HL) mice with only tail suspension treated with vehicle; HU mice with tail suspension treated with vehicle; HU mice treated with PTH; and HU mice treated with ALN. Starting immediately after reloading, vehicle, PTH, or ALN was injected subcutaneously. After a 2-week treatment, mechanical sensitivity was examined using von Frey filaments. Bilateral hind limbs were removed for micro-computed tomography, immunohistochemical analysis, and messenger RNA (mRNA) expression analysis.

Results

HU mice with tail suspension developed bone loss and mechanical hyperalgesia in the hind limbs. The HU mice showed an increased osteoclasts and sclerostin-positive cells in the hind limb bone. Furthermore, PTH and ALN both prevented HU-induced bone loss and mechanical hyperalgesia in the osteoporotic animal models. Histological examination of the hind limb bone revealed that, similar to ALN, PTH inhibited the osteoclasts and sclerostin-positive cells. The mRNA levels of TNFα and IL-6 tended to decrease with ALN or PTH treatment compared with those without any treatment.

Conclusions

Treatment with PTH as well as BP prevented bone loss, mechanical hyperalgesia, osteoclast increase, and osteocyte increase. Similar to BP, the inhibitory effect of PTH on osteoclasts might contribute to the improvement of skeletal pain.

Keywords:

• Teriparatide
• bisphosphonate
• immobility-induced osteoporosis
• skeletal pain

Acknowledgements

The authors would like to thank Takahiro Iino and Katsura Chiba for providing excellent technical assistance. No benefits or funds were received in support of the study.

Authors’ contributions

HW was the principal investigator in this study and was responsible for the original hypothesis, study design, final data analysis, and writing of the manuscript. GM carried out the set of in vivo studies, performed the ex vivo experiments, and reviewed the immunostained sections. NN reviewed the immunostained sections and performed the statistical analysis. SK and TN carried out the in vivo experiments and reviewed the immunostained sections. YN designed the histochemical protocols and performed the staining. AS participated in the design of the study and helped draft the manuscript. All authors read and approved the final manuscript.

Conflict of interest

None.